Brunswick Layover Environmental Assessment (EA)

Appendix G: MaineDEP TMDL Assessment Summary: Unnamed Tributary 

to the Androscoggin (near River Rd.)

September 2013
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Watershed Description 

This TMDL assessment summary applies to a 1.85-mile 

unnamed tributary to the Androscoggin River, located in the 

City of Brunswick, Maine. The Unnamed Tributary begins in 

a wetland area between Old Portland Road (Route 1) and 

Route 295 in Brunswick. The stream flows south across 

Route 1, through a business park along Industrial Parkway 

and then continues in an easterly direction, roughly parallel to 

a busy commercial section of Route 1. Two smaller 

tributaries flow into the stream – one from the north and 

another from the south. The unnamed Tributary flows behind 

numerous businesses along Route 1 before crossing River 

Road and joining the Androscoggin River. The Unnamed 

Tributary watershed covers 749 acres in the City of 

Brunswick. 

 Stormwater runoff from impervious cover (IC) is the 

largest source of pollution and stream channel alteration 

to the Unnamed Tributary. Stormwater falling on roads, 

roofs and parking lots in developed areas flows quickly 

off impervious surfaces, carrying dirt, oils, metals, and 

other pollutants, and sending high volumes of flow to the 

nearest section of the stream. 

 A number of Route 1 storm drains, which are linked 

directly to the unnamed tributary, funnel runoff from 

roads and parking lots down to the stream. 

 Exposed tree roots along the banks the Unnamed 

Tributary and an unstable streambank are signs of 

degraded habitat for life living in the stream. 

 Wetland and woodlands in the north- and south-eastern 

part of the watershed absorb and filter stormwater 

Waterbody Facts

 Segment ID: 

ME0104000210_420R01

 City: Brunswick, ME 

 County: Cumberland 

 Impaired Segment 

Length: 1.85 miles 

 Classification: Class B 

 Direct Watershed: 1.17 

mi2 (749 acres)

 Watershed Impervious 

Cover: 23%

 Major Drainage Basin: 

Lower Androscoggin River

Unnamed Tributary to the 

Androscoggin (near River Rd.) 

TMDL Assewsment Summary 

Definitions

• TMDL is an acronym for Total Maximum Daily Load, 

representing the total amount of a pollutant that a water body 

can receive and still meet water quality standards.

• Impervious cover refers to landscape surfaces (e.g. roads, 

sidewalks, driveways, parking lots, and rooftops) that no longer 

absorb rain and may direct large volumes of stormwater runoff 

into the stream. 

Watershed 

Land Uses

Developed

(20%)

Agriculture 

Wetlands (8%)

(15%)

NonDeveloped

(57%)

Other (2%)

Unnamed Tributary (near 

River Rd.) Watershed 
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pollutants, and help protect water quality in the stream. 

Why is a TMDL Assessment Needed?

The Unnamed Tributary to the Androscoggin River (near 

River Road) a Class B freshwater stream, has been assessed 

by DEP as not meeting water quality standards for aquatic 

life use, and has been listed on the 303(d) list of impaired 

waters. The Clean Water Act requires that all 303(d)-listed 

waters undergo a TMDL assessment that describes the

impairments and establishes a target to guide the measures 

needed to restore water quality. The goal is for all 

waterbodies to comply with state water quality standards. 

The impervious cover TMDL assessment for the Unnamed 

Tributary addresses the water quality impairments to aquatic 

life use (based on stream habitat and benthic 

macroinvertebrate assessments). These impairments are 

associated with a variety of pollutants in urban stormwater as well as erosion, habitat loss and unstable 

stream banks caused by excessive amounts of runoff. 

Sampling Results & Pollutant Sources 

DEP makes aquatic life use determinations 

using a statistical model that incorporates 30 

variables of data collected from rivers and 

streams, including the richness and abundance 

of streambed organisms, to determine the 

probability of a sample meeting Class A, B, or 

C conditions. Biologists use the model results 

and supporting information to determine if 

samples comply with standards of the class assigned to the stream or river (Davies and Tsomides, 2002). 

The stream’s impairment is based on stream habitat assessments. DEP also collected benthicmacroinvertebrate data in 2006 and 2008 at a sampling station downstream of River Road (S-641) 

(Maine DEP, 2010b). Data collected at this station indicates Class B 

the Unnamed Tributary is “non attaining” (NA), meaning it does not 

meet Class A, B, or C conditions. 

Impervious Cover Analysis 

Increasing the percentage of impervious cover (%IC) in a watershed is 

linked to decreasing stream health (CWP, 2003). Because the 

Unnamed Tributary’s impairment is not caused by a 

single pollutant, %IC is used for this TMDL to 

represent the mix of pollutants and other impacts 

associated with excessive stormwater runoff. The 

Unnamed Tributary watershed has an impervious 

surface area of 23% (Figure 1). DEP has found that 

in order to support Class B aquatic life use, the 

Unnamed Tributary watershed may require the 

Unnamed Tributary downstream of River 

Road (Station 641). (Photo: FB Environmental)

8% IC represents an 

approximate 65% 

reduction in stormwater 

runoff volume and 

associated pollutants when 

compared to existing 

pollutant loads. 

Sampling 

Station

Sample 

Date

Statutory 

Class

Model 

Results

S-641 

S-641

8/29/2002 

8/13/2008 

B 

B 

NA 

NA 

Impervious Cover GIS Calculations 

The Impervious Cover Calculations are based on 

analysis of GIS coverage’s presented in Figure 1. 

The impervious area is derived from 2007 

1 meter satellite imagery and the watershed 

boundary is an estimation based on contours 

and digital elevation models. 
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characteristics of a watershed with 8% impervious cover. This WLA & LA target is intended to guide 

the application of Best Management Practices (BMP) and Low Impact Development (LID) techniques to 

reduce the impact of impervious surfaces. Ultimate success of the TMDL will be the stream’s 

compliance with Maine’s water quality criteria for aquatic life. 

Next Steps 

Because Unnamed Tributary to the Androscoggin River (near River Road) is an impaired water, specific 

sources of stormwater runoff in the watershed should be considered during the development of a 

watershed management plan to: 

 Encourage greater citizen involvement (through the Androscoggin River Watershed Council) to 

ensure the long term protection of the Unnamed Tributary; 

 Address existing stormwater problems in the Unnamed Tributary watershed by installing 

structural and applying non-structural best management practices (BMPs); and 

 Prevent future degradation of the Unnamed Tributary through the development and/or 

strengthening of local stormwater control ordinances. 
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Figure 1: Map of Unnamed Tributary to the Androscoggin River (near River Road) watershed impervious cover.
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Figure 2: Map of Unnamed Tributary to the Androscoggin River (near River Road) watershed land cover.
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Unnamed Tributary Watershed Reconnaissance Survey 

A one-day reconnaissance survey of the Unnamed Tributary to the Androscoggin River (near River 

Road) watershed was conducted on October 15, 2010. As shown in Figure 2, the Unnamed Tributary 

originates in a wetland area north of Old Portland Road (Route 1) in Brunswick. The watershed is highly 

developed, with the majority of uses being commercial and industrial. The stream runs parallel to a busy 

commercial section of Route 1 in the northeastern portion of the watershed, and a smaller tributary to the 

stream flows through an area of industrial development in the central part of the watershed. The stream 

is exposed for the majority of its length, but includes some culverted road and railway crossings. The

stream and its smaller tributaries appear to be directly connected to impervious cover in multiple 

locations. 

The goal of the survey was to provide a list of preliminary locations for site-specific stormwater 

mitigation (e.g., structural and non-structural Best Management Practices (BMPs)) in the watershed.

There are many locations in the Unnamed Tributary watershed where stormwater mitigation would be 

beneficial. Six potential stormwater mitigation sites have been selected and are described below to 

demonstrate the types of mitigation that may be appropriate in the watershed. 

Locations of the potential stormwater mitigation sites identified during the reconnaissance survey are

shown in Figure 4 below. 

Figure 4: Locations of potential stormwater mitigation sites in the Unnamed Tributary watershed.
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Site 1 – Route 1 / McDonalds 

Site 1 is located behind the McDonalds building on Route 1. In this reach, the Unnamed Tributary flows 

parallel to Route 1. A steep slope behind the businesses along Route 1 leads down to the stream. At Site 

1, two large culverts, stacked one above the other, emerge from the steep bank behind the McDonalds 

building. These culverts appear to be linked to a storm catchment that drains a portion of Route 1 and

some of the nearby businesses. Where the culverts emerge from the embankment, slope failure and 

erosion has resulted in large amounts of soil entering the stream. At the time of the reconnaissance visit, 

heavily sediment-laden water was flowing under the culverts and directly to the stream in addition to 

stormwater flowing out of the culverts. Approximately 50 feet to the east of the culverts, a concrete 

sluiceway appears to drain the McDonald’s parking lot. Runoff from the lot flows down the outfall and 

into the stream untreated. 

Along this stream reach, similar steep slopes with embankment erosion were noted behind other 

businesses as well, in addition to trash and yard waste debris. Thus, this entire reach of river should be 

evaluated for potential mitigative BMP implementation. Several types of invasive species also grow 

thickly along the banks, including Japanese knotweed, Japanese barberry, multiflora rose, and 

bittersweet. 

Figure 5: Location of potential stormwater mitigation Site 1behind McDonalds on Rte 1. 
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Types of stormwater mitigation that may be appropriate for this site include: 

1. Retrofit Reconnaissance Inventory (RRI). An RRI survey of the commercial businesses 

draining to the outlet at this site would support characterization and reduction of excessive 

stormwater flow volumes reaching the stream from this location. This type of survey includes a 

rapid field assessment of potential stormwater storage and on-site retrofit sites in the area. 

Retrofits provide stormwater treatment in locations where practices previously did not exist or 

were ineffective, and include modification to existing stormwater practices or construction of 

new practices. Typical sites that may be investigated for possible retrofitting include culverts, 

storm drain outfalls, highway rights-of-way, open spaces, parking lots, and existing detention 

ponds. 

2. Rock rip-rap and native vegetation. Stabilizing bare soil on the steep slopes surrounding the 

culverts at Site 6 with stone rip-rap and native vegetation would help to reduce impacts to water 

quality at the site. Riprap is a permanent, erosion-resistant ground cover constructed of large, 

loose, angular or rounded stone. Its purpose is protecting the soil surface from the erosive forces 

of concentrated runoff; to slow the velocity of concentrated runoff while enhancing the potential 

for infiltration; and to stabilize steep slopes. It should be used in combination with native 

vegetation plantings to shade the stone and protect against increasing stream temperature. 

3. Check dams. A check dam is a small dam built across a minor channel, swale, or drainage ditch. 

Building check dams across the existing channel draining the McDonald’s lot would help lower 

the speed of water flow during storm events and allow sediments and pollutants to settle. 

4. Plunge pool. A plunge pool at the outfall of the concrete channel and/or culverts would help to 

dissipate the velocity of stormwater runoff and provide some pretreatment.

Site 1 Photos: Storm drain on Route 1 that is linked to the culverts behind McDonalds (left; view of area 

draining to the storm drain (middle); stacked culverts behind McDonalds (right). 
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Site 1 Photos, continued: View from above of failed bank surrounding the culverts (upper left); sedimentladen water flows under culverts (upper right); sediment laden water entering stream (bottom left); 

concrete sluiceway draining McDonalds lot (bottom right). 

Sediment-laden water 

entering stream 
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Site 2 – Hancock Lumber, Church Road 

Site 2 is located at the Hancock Lumber property off of Church Road (Figure 6). The property is situated 

adjacent to the headwaters of the small stream that flows into the Unnamed Tributary, and consists of a 

main building and paved parking area in front and a large unpaved lot with several small outbuildings in 

back. 

Two separate locations on the property were noted during the reconnaissance visit: 

• Site 2A: On the northeastern side of the property, a large portion of the unpaved lot drains into a 

storm drain which outlets into the nearby stream. Because the soil around the drain is not 

stabilized, sediment and debris flow freely into the drain and the stream. Nearby, overland flow 

from the portions of the unpaved lot drains directly to the stream, which has little to no vegetated 

buffer to help filter sediment. 

• Site 2B: On the northwestern side of the property, overland flow from the unpaved lot and roof 

runoff drains directly to the stream. Large pieces of trash were also noted in the stream nearby. 

Figure 6: Location of potential stormwater mitigation Site 2 at Hancock Lumber off Church Rd. 

Blue arrows indicate direction of direct flow to stream. 
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Types of stormwater mitigation that may be appropriate for this site include: 

1. Stabilize bare soil. Stabilizing bare soil in the unpaved lot and around the storm drain at Site 2A 

will greatly reduce impacts to water quality at the site. A coarse gravel surface material could be 

used to resurface the lot. With the high amounts of traffic at the site, regular maintenance is 

critically important. 

2. Redirect flow. The unpaved lot could be regraded to direct stormwater flow away from the 

stream to a grassed swale, detention basin and/or rain garden. 

3. Vegetated buffers. Plant to increase the buffer strip of native vegetation adjacent to the stream. 

Vegetated buffers slow stormwater runoff, provide an area where runoff can permeate the soil, 

contribute to ground water recharge, and filter sediment. Slowing runoff also helps to prevent 

soil erosion and streambank collapse. 

4. Redirect flow. Stormwater flowing directly from roofs and unpaved parking lots should be 

redirected and hydrologically disconnected from the stream. This could be accomplished by 

regraded to direct stormwater flow away from the stream to a grassed swale or infiltration 

gallery. 

Site 2A Photos: A storm 

drain surrounded by 

unstabilized soil drains the 

unpaved lot, delivering 

sediment and debris to the 

stream (left). Portions of the 

unpaved lot drains through an 

unvegetated passage directly 

to the stream (right). 

Site 2B Photos: Runoff from 

the unpaved lot and from 

nearby structure roofs drains 

to the stream (left). Sedimentladen water flows directly to 

the stream (right). 
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Site 3 – Industrial Parkway

Site 3 is located on Industrial Parkway, 

just south of the property at 4 Industrial 

Parkway (Figure 7). As shown in the 

photographs below, a curb cut leads to a 

~15 foot long metal half-culvert at this 

site. Runoff from the roadway and 

adjacent commercial building flows 

down the culvert and directly to a 

stream. The invasive Japanese 

knotweed was also noted at the site. 

Types of stormwater mitigation that 

may be appropriate for this site include: 

1. Rock rip-rap and native 

vegetation. Replacing the metal 

culvert at Site 3 with a channel 

of rock rip-rap interspersed with 

native vegetation would help to 

slow water flow and filter 

sediments. Riprap is a 

permanent, erosion-resistant ground cover constructed of large, loose, angular or rounded stone. 

Its purpose is protecting the soil surface from the erosive forces of concentrated runoff; to slow 

the velocity of concentrated runoff while enhancing the potential for infiltration; and to stabilize 

steep slopes. It should be used in combination with native vegetation plantings to shade the stone 

and protect against increasing stream temperature. 

2. Plunge pool. A plunge pool at the channel outlet would allow the dissipation of energy filtration 

of sediment before water enters the stream. 

Site 3 Photos: Stormwater from Industrial Parkway drains to a road curb cut (left and middle) which leads to a 

metal half-culvert (right) that channels water to the stream. 

Figure 7: Location of potential stormwater mitigation Site 3 

near 4 Industrial Parkway.
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Site 4 – LL Bean Warehouse, Industrial Parkway

Site 4 is located at the LL Bean warehouse off 

Industrial Parkway in the central part of the 

watershed (Figure 8). The property is located 

adjacent to a small stream that flows into the 

Unnamed Tributary (Figure 8). Although much 

of the stormwater runoff from this property is 

directed to a stormwater detention pond, the 

existing treatment does not capture all of the 

stormwater on the property. Specifically, some of 

the stormwater drains to the northeast corner of 

the property. Here, stormwater flows across an 

area of bare soil and down an eroding channel 

that leads directly to the stream. Additionally, an

uncovered dumpster was noted at the northeast 

corner of the building. Runoff from the dumpster 

was noticed nearby. 

Types of stormwater mitigation that may be appropriate for this site include: 

1. Good housekeeping. Implementation of aggressive street sweeping, catch basin cleanout and 

other good housekeeping measures in the parking lot will help reduce pollutant loads by 

removing materials from impervious surfaces prior to storm events. The dumpster should also 

remain covered at all times. 

2. Plant vegetation. The area of bare soil in the northeast corner of the lot is a good location for a 

grassed swale or rain garden that would help capture and detain runoff. A rain garden is a planted 

depression that allows rainwater runoff from impervious urban areas like roofs, driveways, 

walkways, parking lots, and compacted lawn areas the opportunity to be absorbed. This reduces 

rain runoff by allowing stormwater to soak into the ground. 

3. Stabilize ditch. The existing eroding ditch on the northeast corner of the property could be 

stabilized with vegetation or stone rip-rap to prevent further erosion. 

Site 3 Site 3

Figure 8: Location of potential stormwater 

mitigation Site 4 at LL Bean off Industrial Pkwy.

Site 4 Photos: An uncovered dumpster is located near the NE corner of the building (left). Stormwater flowing 

over ran area of bare soil (middle) leads to an eroding ditch (right) which flows directly to the stream. 

A rain garden would 

help filter sediment and 

stabilize bare soil. 
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Site 5 – Owens Corning Industrial Building, Bibber Parkway

At Site 5, the Unnamed Tributary flows around the Owens Corning building off of Bibber Parkway 

(Figure 9). During rainstorms, large amounts of rainwater flow off the roof and pavement at the Owens 

Corning property. Most of this stormwater runoff is directed to treatment systems such as a large 

stormwater detention pond and rock-lined ditches. However, two locations on the property were noted as

having either inadequate or non-existent stormwater treatment in place. 

• Site 5A: On the back side of the Owen’s Corning building, a large volume of water flows off the 

roof during rain storms. A rock lined swale on the back side of the building directs some of the 

flow to a stormwater detention pond. However, during the reconnaissance visit, it was noted that 

instead of being filtered through the rock swale, some of the rainwater pools nearby, creating an 

erosive channel that flows into the woods above the stream rather than flowing into the detention 

basin. This problem seems to be due to inadequate maintenance of the treatment system.

• Site 5B: On the front side of the building, flow from a building drainage pipe has created an 

eroding channel that flows down the driveway and eventually into a grass-lined ditch that is also 

eroding. Water from this ditch then flows past the Bibber Parkway pump station, and sedimentladen water flows directly to the stream. 

Types of stormwater mitigation that may be appropriate for Site 5 include: 

1. Maintain and inspect existing BMPs regularly. Properly conducted inspections and 

maintenance ensure that BMPs function properly and help prevent pollution discharges. 

Figure 9: Locations of potential stormwater mitigation Sites 5A, 5B and 6 off of 

Bibber Parkway.
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Infiltration systems in particular should be inspected several times in the first year of operation 

and at least annually thereafter. Conduct the inspections after large storms to check for surface 

ponding near the inlet that may indicate clogging (e.g. Site 5A). 

Additionally, implementation of aggressive street weeping, catch basin cleanout and other good 

housekeeping measures in the driveway and parking lot will help to reduce pollutant loads by 

removing materials from impervious surfaces prior to storm events.

2. Improve ditches. At Site 5B, adding a rock-lined catch basin or plunge pool at the drainage pipe 

outlet and check dams to the grass swale would help slow and filter stormwater, thus reducing 

erosion issues. From the pump station down to the stream, lining the ditch with rock rip-rap 

would further reduce the chances of sediment-laden water reaching the stream. 

3. Redirect flow. Stormwater flowing directly from roofs and parking lots should be redirected and 

hydrologically disconnected from the stream. This could be accomplished by regraded to direct 

stormwater flow away from the stream to a grassed swale, detention basin or rain garden. 

Site 5A Photos: Stormwater runoff pools behind the Owen’s Corning building (left); water pools at the 

detention basin inlet (middle); excess runoff results in an eroding channel (right). 

Sediment buildup

Site 5B Photos: Flow from the drainage pipe creates an eroding channel (left); the flow then leads to an 

eroding grass-lined swale (middle); runoff flows in a channel parallel to the road to the stream (right). 

Lining the ditch with rocks would 

help slow flow and filter sediment.

Check dams would help slow flow 

and filter sediment. 
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Site 6 – Ouellette Associates General Contractors, Bibber Parkway

Site 6 is situated immediately downstream of Site 5 (Figure 10). From the Owens Corning property, the 

Unnamed Tributary flows under Bibber Parkway and past a property owned by Ouellette Associates 

(Figure 10). Behind the Ouellette office building, a large paved area is located adjacent to the stream. 

The steep slope leading from the paved area to the stream is stabilized with rock rip-rap. However, much 

of the runoff from the roof and paved appears to reach the stream untreated. Roof and paved-area runoff 

flows to a storm drain on the eastern corner of the property, which outlets from a culvert in the steep 

bank near the stream. Contracting equipment and machinery is stored uncovered on the paved area. This

equipment and any associated pollutants would flow directly to the stream during rain events. 

Site 6 Photos: Runoff from paved surfaces (upper left) and the building rooftop (upper right) drains to a 

stormwater drain in the back corner of the property (bottom left). The drain outlets from a culvert adjacent to the 

stream (bottom right). 
17 

Types of stormwater mitigation that may be appropriate for Site 6 include: 

1. Good housekeeping. Implementation of aggressive street sweeping, catch basin cleanout and 

other good housekeeping measures in the parking lot adjacent to the stream will help reduce 

pollutant loads by removing materials from impervious surfaces prior to storm events. 

2. Covered storage. Providing a covered storage area for machinery and supplies may reduce 

pollutants being washed into the stream via stormwater.

3. Sediment basin. There are many techniques available to capture and route the runoff to an 

appropriately designed discharge location. The goal of these systems is to reroute harmful 

stormwater flows to areas where water can infiltrate to groundwater or receive treatment prior to 

entering the stream. One option at Site 6 would be the installation of a sediment basin or plunge 

pool at the storm drain outlet to allow sediment to settle out before the runoff is discharged to the 

stream. 

4. Redirect flow. Stormwater flowing directly from roofs and parking lots should be redirected and 

hydrologically disconnected from the stream. This could be accomplished by regraded to direct 

stormwater flow away from the stream to a grassed swale, infiltration gallery or rain garden. 

References

Center for Watershed Protection (CWP). 2003. Impacts of Impervious Cover on Aquatic Systems. 

Watershed Protection Research Monograph No. 1. Center for Watershed Protection, Ellicott 

City, MD. 142 pp. 

Davies, Susan P. and Leonidas Tsomides. 2002. Methods for Biological Sampling and Analysis of 

Maine’s Rivers and Streams. Maine Department if Environmental Protection. Revised August, 

2002. DEP LW0387-B2002. 

Maine Department of Environmental Protection (DEP). 2010a. Draft 2010 Integrated Water Quality 

Monitoring and Assessment Report. Bureau of Land and Water Quality, Augusta, ME. DEPLW1187. 

Maine Department of Environmental Protection (DEP). 2010b. Assessment Database Detail Report for 

the Unnamed Tributary to the Androscoggin River (new River Road). Bureau of Land and Water 

Quality, Augusta, ME.